Compress PDF Online in Seconds
Pick a quality preset, or set an exact target size in KB or MB and we'll get as close to it as we can — free, no sign-up required.
Drag & drop your PDF here
or click to browse from your computer
Max 100MB per upload
How much do you want to shrink it?
Preparing...
Original
Compressed
Hit an exact size
Type a target in KB or MB and we'll search for the closest quality setting that fits it.
Smarter than a zip
We re-encode the images inside your PDF instead of just wrapping the file, so it actually shrinks.
Completely free
Compress as many PDFs as you like, up to 100MB per file, with no sign-up required.
How to Compress a PDF
- Upload your PDF. Drag it into the box above or click to browse. Files up to 100MB.
- Choose how to compress it. Pick a quality preset (High Quality, Recommended, or Extreme Compression), or switch to Custom Target Size and enter an exact KB or MB target.
- Click Compress. Processing happens on our server and takes a few seconds for most files.
- Download your smaller PDF. You'll see the original and new file size side by side, with the percentage reduction.
What Does PDF Compression Actually Do?
A PDF's file size mostly comes down to what's inside it — and images are almost always the biggest factor. A scanned document, for example, is really just a series of high-resolution photos wrapped in a PDF file, which is why scanned PDFs are often much larger than PDFs made from typed text.
Compressing a PDF works by re-encoding the images inside it at a smaller size and lower quality, and cleaning up unused data in the file's structure. A PDF made entirely of typed text with no images will shrink a little from that structural cleanup — a scanned or photo-heavy PDF will shrink a lot more, because there's simply more image data to work with.
Choosing a Compression Level
Custom Target Size
If you need a file under a specific size — a 5MB email attachment limit, a 500KB upload cap on a job portal — enter that target directly in KB or MB instead of guessing which preset gets you there. CurePDF works through a range of compression settings automatically to get as close to your target as it safely can. If your target is smaller than what's realistically achievable without seriously degrading the images, you'll get the smallest safe result instead, with a note explaining that.
Quality Presets
- High Quality — light compression, smallest quality drop. Best when you still want the file usable for print or close-up viewing.
- Recommended — a solid size reduction while keeping everyday quality. This is the default, and works well for most documents.
- Extreme Compression — the smallest possible file. Images will look noticeably softer, a reasonable trade when file size matters more than image sharpness.
Will Compression Affect My PDF's Quality?
Yes, to some degree — that's inherent to any real compression, not just CurePDF's. Compression reduces image resolution and re-encodes images at a lower quality setting to shrink file size. Text stays sharp regardless of the level you choose, since compression works on images, not on the text itself. At High Quality, the difference is usually hard to notice. At Extreme Compression, images will visibly soften — that trade-off is the whole point of that setting.
If your PDF has no images at all — a typed report or contract, for example — compression will only reduce file size slightly, from cleaning up the file's internal structure, since there's no image data to compress.
Why Is My PDF File So Large?
The most common reasons: it's a scanned document (each page is effectively a high-resolution photo), it contains many embedded images, or it was created by a tool that didn't optimize images before embedding them. If your PDF is already small and mostly text, don't expect a dramatic size drop — there isn't much to compress in a file like that to begin with.
When You'd Compress a PDF
Email attachments
Get under a size limit that's bouncing your message back.
Application portals
Meet strict upload limits on job or government sites.
School submissions
Fit assignment or application uploads under a size cap.
Scanned paperwork
Shrink scans that came out far larger than the original.
Business documents
Send files quickly without a slow upload on either end.
Cloud storage
Free up space and sync faster with smaller files.
Compress PDF on Mobile
CurePDF's compressor works in your phone's browser — Chrome, Safari, or any modern mobile browser on Android or iPhone/iPad — the same way it does on desktop. There's no separate app; you use the same page, and the upload/download flow works the same with touch as it does with a mouse.
Is It Safe to Compress a PDF Online?
Your file is processed on our server and never written to permanent storage — it's handled in memory for the compression itself. Per CurePDF's Privacy Policy, uploaded files are automatically deleted within 1 hour. We don't review, share, or otherwise use the contents of your files beyond performing the compression you requested. As with any online tool, avoid uploading documents with highly sensitive information, like government IDs or financial account details, unless you're comfortable with standard web-based processing.
Frequently Asked Questions
How do I compress a PDF?
Upload your file, choose a quality preset or set a custom target size, and click Compress. Your smaller PDF downloads automatically.
How can I reduce PDF file size?
The same way — compress it using a quality preset, or set an exact size target if you need to hit a specific limit, like an email attachment cap.
Can I compress a PDF online for free?
Yes. CurePDF's compressor is free to use, with no account required.
How much can a PDF be compressed?
It depends entirely on what's inside it. Image-heavy or scanned PDFs can shrink significantly; a PDF that's mostly typed text will only shrink a little, since there isn't much image data to compress.
Does PDF compression reduce quality?
It can reduce image quality, depending on the level you choose — text stays sharp at every level. High Quality keeps the difference minimal; Extreme Compression trades visible image sharpness for the smallest file.
Can I compress a large PDF?
Yes, up to 100MB per file.
How do I compress a PDF for email?
Use Custom Target Size and enter your email provider's attachment limit, often around 25MB or lower — CurePDF will get as close to that as it safely can.
Can I compress a scanned PDF?
Yes — scanned PDFs are usually the best candidates for compression, since each page is effectively a photo and photos are where most of the size reduction comes from.
Can I compress a PDF on my phone?
Yes, it works the same in a mobile browser as it does on desktop.
Is it safe to compress a PDF online?
Your file is processed and not permanently stored — per CurePDF's Privacy Policy, uploads are automatically deleted within 1 hour, and file contents aren't reviewed or shared.
Why is my PDF file so large?
Usually because it's scanned, contains many embedded images, or those images weren't optimized before being added to the PDF.
Can I compress a PDF without losing quality?
Some quality change is unavoidable with any real compression — but at the High Quality preset, the difference is usually hard to notice. Completely lossless compression would only shrink a file slightly, since it couldn't touch image data at all.
What's the difference between PDF compression and reducing image quality?
For CurePDF, they're closely related — compression mainly works by reducing the resolution and quality of the images inside your PDF. It also cleans up unused data in the file's structure, which helps even PDFs with no images at all shrink slightly.